全新java初学者实践教程6(Java SE5.0版)
2]I4M[|&z 基本语法3
Cnnh7` rE iKi ~oI1zNz/ 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
n/DP>U$I& N<f"] [font="Times] 1.循环语句[font="Times]:while,do-while,for
qgE 73.!`6 /nyUG^5#{ [font="Times]2.分支语句[font="Times]:if-else,switch,
4S,`bnmB [font="Times]
^cV;~&|.Xk 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
hD\rtW [font="Times]
2GFLnz 4.异常处理语句[font="Times]:try-catch-finally,throw
pM x =2[7
E 实践:
EzDk}uKY0R [font="Times] 1.循环语句
r9X?PA0f [font="Times] while 语句
Ae
mDJ8Y [font="Times]class While {
J+[_Wd [font="Times]public static void main(String args[]) {
"nZ*{uv [font="Times]int n = 10;
wyp|qIS; [font="Times]while(n > 0) {
iDMJicW!+F [font="Times]System.out.println("tick " + n);
SPN5dE.@ [font="Times]n--;
"vXxv'0\f [font="Times]}
Tg!i%v(-t [font="Times]}
xG}(5Tt [font="Times]}
A{UULVp [font="Times] do…while 语句
y(Y!?X I [font="Times] class DoWhile {
{8 8 )~ [font="Times]public static void main(String args[]) {
eyefW n& [font="Times]int n = 10;
NZ;{t\ [font="Times]do {
fYp'&Btb]x [font="Times]System.out.println("tick " + n);
D|@/yDQ [font="Times]n--;
JmPHAUd [font="Times]} while(n > 0);
/3A^I{e74
[font="Times]}
HkQ*y$$ [font="Times]}
W`K7 QWV4 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
MHSs!^/g5 [font="Times] for语句
/<E5"Mm% [font="Times] class ForTick {
7.C;NT [font="Times]public static void main(String args[]) {
*4_jA]( [font="Times]int n;
!xP8#|1 [font="Times]for(n=10; n>0; n--)
5Ycco,x [font="Times]System.out.println("tick " + n);
iOwx0GD.n [font="Times]}
n.wF&f'D] [font="Times]}
n,=VQOu 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
I([!]z 还有啊,[font="Times]for循环的部分可以为空的
=g/{%; [font="Times]class ForVar {
k9$K} [font="Times]public static void main(String args[]) {
Mzsfo;kk+ [font="Times]int i;
=3q/F7- [font="Times]boolean done = false;
C3< m7h [font="Times]i = 0;
8i6Ps$T [font="Times]for( ; !done; ) {
v[#9+6P= [font="Times]System.out.println("i is " + i);
hfnN@Kg?B} [font="Times]if(i == 10) done = true;
_$=
_du [font="Times]i++;
.gG1kW A- [font="Times]}
R>,:A%?^b5 [font="Times]}
io,M{Ib [font="Times]}
循环语句的例子下载 hJwC~HG5 [font="Times] 2.分支语句[font="Times]
D_/^+H]1 [font="Times] if/else语句
+6UVn\9Q [font="Times]class IfElse {
At flf2 K [font="Times]public static void main(String args[]) {
S>.SSXlM [font="Times]int month = 4; // April
Q@
2i~Qo[ [font="Times]String season;
(Q%'N3gk [font="Times]if(month == 12 || month == 1 || month == 2)
~\=1'D^6CK [font="Times]season = "Winter";
7:9.&W/KE [font="Times]else if(month == 3 || month == 4 || month == 5)
L !=4N!j [font="Times]season = "Spring";
_7IKzUn9g[ [font="Times]else if(month == 6 || month == 7 || month == 8)
)N=NR2xBZ [font="Times]season = "Summer";
D<8HZ%o [font="Times]else if(month == 9 || month == 10 || month == 11)
AK\$i$@6 [font="Times]season = "Autumn";
+|bmT [font="Times]else
AgV G`q [font="Times]season = "Bogus Month";
>y.%xK [font="Times]System.out.println("April is in the " + season + ".");
(WK&^,zQn [font="Times]}
[
j3&/ [font="Times]}
f@8>HCI [font="Times]//这段程序输出[font="Times]:
Vl_:c75" [font="Times]//April is in the Spring.
}@Ge}9$h [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
'a$Gv&fu [font="Times] switch语句
hGd<<\ [font="Times] class Switch {
@)
s,{F [font="Times]public static void main(String args[]) {
F;=4vS]\ [font="Times]int month = 4;
"`M?R;DH [font="Times]String season;
>tO`r.5u9 [font="Times]switch (month) {
RY c!~Wh~Y [font="Times]case 12:
t]$P 1*I [font="Times]case 1:
Eq$&qV-?( [font="Times]case 2:
w4W_iaU [font="Times]season = "Winter";
vz^<YZMu [font="Times]break;
vk*=4}: [font="Times]case 3:
*H?!;u=8 [font="Times]case 4:
Gp4A.\7 [font="Times]case 5:
N5]0/,I} [font="Times]season = "Spring";
}b=}uiR# [font="Times]break;
:T]o) [font="Times]case 6:
xEf'Bmebk [font="Times]case 7:
VYt!U [font="Times]case 8:
sXi=70o [font="Times]season = "Summer";
}-~X4u# [font="Times]break;
yHHt(GM|o [font="Times]case 9:
#{k|I$ [font="Times]case 10:
f>piHh? [font="Times]case 11:
h3*Zfl<] [font="Times]season = "Autumn";
)dY=0"4Z [font="Times]break;
3l3+A+n [font="Times]default:
%=?cZfFqO [font="Times]season = "Bogus Month";
jV?
}9L^; [font="Times]}
PQK(0iCo4 [font="Times]System.out.println("April is in the " + season + ".");
k]5Bykf`Ky [font="Times]}
SVv;q?jZ [font="Times]}
分支语句代码下载 TJ:]SB h~(G$':^ [font="Times]switch语句适合于条件非常多的逻辑
krsYog(^z 请看上述语句可以混合使用,请看
下载例子